Grinding mill



May 1 9, 1925.

W. FOWLER GRINDING MILL Filed July 1923 2 Sheets-Sheet 1 May 19, 1925.

Waller Fowler 4? I flilorniy-fi Patented l llay 19, 1925.

UNITED STATES 1,538,791 PATENT OFFICE.

WALTER FOWLER, or LONDON, ENGLAND.

GRINDING MILL.

'1 all whom it may concern:

Be it known that I, WALTER Fownnn, a

subject of the King of England, residing at London, England, have mvented certain 7 new and useful Improvements in Grinding Mills, of which the following is a specification.

frictional engagement with the said first member.

This invention comprises a grinding mill of the type described wherein the grinding surfaces are of spherical curvature about the same centre, and are rotatable about fixed axes inclined to one another.

According to another feature of this invention, the operative surface of the positively driven grinding member subtends a solid angle of 90 degrees, and the second member which is driven frictionally from the first member, is smaller, for example, the greatest length of chord on it is about five-sixthsofthe length of the corresponding chord of the first member, and the axis of rotation of the'second member is inclined to the axis of rotation of the first member by such an amount that their peripheral edges coincide at one point.

Provision may be made for adjusting the axes of rotation of the two grinding members relatively to one another if so desired, it being appreciated that once the adjust ment has been made theaxes remain in the same relative positions throughout the grinding operation,and that there is no contiuuous or automatic adjustment of the axes relatively to one another during the opera tion. r

Other details of the invention will be hereinafter described with reference to a specific embodiment thereof, and the novel features pointed out in the claims appended to this specification.

In the accompanying drawings- Figure 1 is a side elevation in central section of a grinding mill according to this invention i Application filed. July 28,

1923. Serial No. 654,460.

Figure 2 is a sectional view of one of the grinding elements, being a section on the line 22 of Figure 3; i t

Figure 8 is a view looking on the underside of the grinding element shown in Figure 2;

Figures 4 .and 5 are detail views on the lines 4l-t and 5-5 of Figure 3; and

Figure 6 shows a detail of the mounting of theuppcr grinding-mei'nber.

Like reference characters indicate like parts throughout the drawings,

Referring first to Figure 1, the machine comprises a suitable frame 10 provided with bearings 11, 12 for a vertical shaft 18. The

shaft may be supportedin any convenient manner, conveniently by a pin 14 in its lower end, formed with a rounded end engaging a similar pin 15 screwed into a convenient part of the machine. The height of the shaft 13 can be adjusted if desired by means of the pin 15.

This shaft has secured upon it a bevelwheel 16 which meshes with and'is driven by another bevel-pinion 17 mounted on a horizontal shaft 18, and this latter shaft also carries fast-anddoose-pulleys 19, for a belt drive, or is otherwise connected in any suitable manner to appropriate driving means.

At the upper end of the shaft 13 there is mounted a grinding member 20. This memher which is rotatably secured to the shaft is formed with its upper surface 21 of a spherical curvature, the centre of curvature lying on the axis of rotation of the shaft 13. Preferably the proportions of the member 20 are such that its spherical surface 21 subtends a solid angle of about degrees, and this member may be formed of any convenient or desired thickness to make provision for Wear.

In the form illustrated, this member is made of stone, such as granite, and it is secured to the shaft by means of a socketmember 22 whichis Sunkinto a central open ing on the stone and is secured centrally therein in any convenient manner, as for ex: ample,,by aligning it correctly and then aouring in cement. The socket may be ormed with projections to engage the stone and provide a positive driving connection andis itself bored to fit on the upper endof the shaft. The shaft may be tapered if so desired, or provided with a key or keys.

A sheet-metal casing 23 is arranged to encircle thegrinding-member 20 completely, and preferably extends above the upper peripheral edge of this member so as to catch any material thrown oif it during rotation.

The lower 'end of the casing is open as at' 24, and is provided with a convenient chute 25.

Upon the frame 10 there is mounted-an upstanding bracket 26 which has pivoted on it at its upper end 27 a pair of members 28 which extend across the grinding niemher. At their free ends these members are connected by tie-rod 29-which is bored to receive a screw-threaded spindle 3O piv'otally mounted on a rod 31 carried on brackets 32 upstanding-from" t-hefr amelO. A hand-wheel 33 provided with alocking-nut -34 engages the screw-threaded spindle so "39, which is-made of stone or any other desired material and is in the form of a cap being spherically curved units under concave face, to the same radius astlre grinding member-20.

It will be seenthat'if the members28 (Figure 6) are swung upwards, the springs 56 will be compresse d sojas to takepart of the weight of the'element 39land thereby reduce the (pressure which it exerts on the lowerelement 20. ripointer and scale are provided on the member 28 and'block 55,'and

the scale is calibrated in any convenient .manner to indicate the pressure exerted by the element on the element'QO, or in other words, 'to indicate the grinding pressure. The member39 is secured onthe rotatable hollow shaft 38 in any convenient "ordesired manner, and'tlietrunnions '86 are so disposed that when the two grindingelements are in engagement/withone another their axes of rotation are" not inthe same straight line, 'butare slightly inclined "to one another. The -grinding surfaceof'the member 39 is somewhat smaller-than that of themember 205 being, for example such that the ratio of ,the lengths of their chords is as5 isto 16, and thetrunnions 36 areso disposed that when the grinding "members are incontact with one anothertheir "pe ripheral edges are substantially co-incident as shown at the left 'hand side of Figure 1.

Since the grinding member 39 is free to 1'0- tate about its own axis, when a drive is imparted to the member 20, the frictional engagement "between thetwo members transmits a drive to the member 39, but owing to its obliquity and eccentricity there is a relative rubbing or grinding movement between the two surfaces in contact with one another.

The grinding member 39 is further illustrated in Figures..,'3, L and 5. Its concave spherical grinding face to is providedyith two series of'groovesor channels. 8 One series extend from the inner edge'of' the grinding surface, as. shown at'tl, in a radial d'irection and aretapered fronrtlie inner to the outer ends. section, as shown'in' Figure'5, but it is not symmetrical, the edge 42; which leads inthe direction of rotation, being substantially a right-angled edge whilst the trailing edge 43 is oblique. Each of the grooves 41 has-a branch 44- extending "laterally from it' on -tl12ttS1Cl6 which is rearwards in the direction of rotation. These constitute the inlet passages for'the material to beground, as hereinafter described.

*There arealso provided outlet passages 45 which extend in a substantially radial-direc tion from the outer-periphery of the: grin dingsurface, and these grooves are symmetrical in their cross-section as' shown in Fig 'ure 4,-taper1n'g from' their .outer to their inner ends. Thegrin'ding'element 39 is secured upontlierotatable hollow"sliaftj38 in such amanner that communication is pr0-- vided' from'theinteri'or ofthe shaft to the inlet/"grooves 41, 4-4, so that material fed in through the shaft'c'a'n pass by way of these grooves in between the grinding surfaces.

'lhe-tapering edge 43 aforesaid" of the inlet grooves men the traihngside, HPOYdQY'tO facilitate the entryof the material between the grinding surfaces,'-and the trailing passages l-nlsoserve the same purpose. The

grinding takes place between the two spherical contacting surfaces, and tlieiiniterm-l when ground is collected in the outlet grooves$5,;andsubsequently delivered to the periphery of the member '39. It spreads over the "whole surfaceof the lower grinding member "20, and is 1 collected tllGl'GlTOlll by meansof *any convenient form of scraper L6-which-del1vers itto the chute This scraper may be mounted i in any 'convmiient manner, being, for example, as indicated carried by an upstanding arm 47 on the frameqnember -48.

A platform orstandmay be providedon the members28ftoreceive-a vessel 49 which containsthe m aterial tobe ground. As illustrated. this vessel is provided with a sloping bottom 50, which leads down to a chute 51, andayalve -is provided iirtlievessel to control the outlet therefrom, the valve being operated by the screw-threaded spindle 52.

The groove is of curved crosslow shaft 38 to introduce the material into the mill.

In the operation of this mill, the parts are arranged as illustrated in Figure 1, and the material to be ground is fed from the vessel 49 through the hollow shaft 38 and inlet passages 41, 4st between the grinding surfaces. It is collected from the surface 21 of the lower element by the scraper 46 and delivered through the chute 25. When it is de sired to clean the mill, the vessel 4:9 is removed, the hand wheel 33 is also removed, and the members 28 can then be swung up, carrying with them the upper grinding member 39. The ends 53 of these members 28 engage a stop 54 on the frame-member 26 to retain the parts in convenient position, and then both of the grinding surfaces are fully exposed and easily accessible. WVhen the parts are replaced, the degree of fineness to which it is required to effect the grinding is determined by screwing down the handwheel 38 to a greater or less extent, to vary the pr ssure between the grinding surfaces.

If it desired, provision may be made for I altering the obliquity of the axis of rotation of the grinding member 39, for example, by arranging that the frame member 26 can be swung about a horizontal axis. It will be appreciated that in a grinding mill constructed in accordance with this invention, the wear is distributed uniformly over the whole of each of the grinding surfaces, so that they maintain their true spherical surfaces, and never require to be trued up, as is the case with other forms of mill. More over, owing to the fact that the drive is transmitted frictionally from one element to the other, a certain amount of slip takes place, and this assists in maintaining uniformity of wear.

The form of the grinding surfaces hereinbcfore described, and illustrated, is suitable for grinding such materials as paints, but this invention also covers other forms of grinding surfaces, according to the materials which are to be treated. Thus, for example, instead of using smooth spherical surfaces, these surfaces might be corrugated, cam concentrically with its own axis, if so desired, and all such modifications are held. to lie within the scope of this invention.

lvhat I claim as my invention and desire to secure by Letters Patent is:-

l. In a grinding mill, the combination of a spherically-curved grinding element, means for rotating it about an axis passing through its centre of curvature, a second grinding element curved concentrically with the first element and bearing frictionally thereon, said second element being rotatable about an axis which is inclined to the axis of rotation of the first element and being driven frictionally thereby.

2. In a grinding mill, the combination of a convex spherically-curved grinding element whereof the spherical surface subtends a solid angle of 90 degrees, means for rotat ing said element about a fixed axis which passes through its centre of curvature, a concave concentrically-curved grinding element subtending a smaller solid angle than the first element, resting upon the first element and rotatable about an axis inclined to the axis of rotation of the first element.

3. In a grinding mill, the combination of a convexly-curved spherical grinding ele ment that is symmetrical and rotatable about a vertical axis, a concave concentrically-curved grinding element resting there on and rotatable about an axis inclined to the axis of the first element, means for rotating the first element, and means for indicating the pressure exerted by the second grinding element on the first grinding element.

4. In a grinding mill, the combination of a convexly-curved spherical grinding element that is symmetrical and rotatable about a vertical axis, a concave concentrically-curved grinding element resting thereon and rotatable about an axis inclined to the axis of the first element, means for rotating the first element, resilient means for raising the second grinding element from the first grinding element and means for indicating the pressure exerted by the said resilient means, substantially as set forth.

5. In a grinding mill, the combination of a vertical shaft, means for rotating it, a convex spherically-curved grinding element secured symmetrically upon the upper end of said shaft, a concave grinding element of equal curvature but smaller diameter resting on the convexly-curved surface with its peripheral edge at one point lying substantially on the peripheral edge of the lower grinding element, a shaft inclined to the said vertical shaft whereon said upper grinding element is rotatable, compression springs supporting said inclined shaft, a lever supporting said springs, means for adjusting said lever to vary the pressure exerted by the upper element on the lower element, and means for suliiplying material to be groundto a central cavity in the up per grinding element.

In testimony whereof I aliix my signature.

IVALTER FOWLER.

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